1. Field of the Invention
The present invention relates to an ambient light detection device and a method of detecting a level of ambient light, in particular for use with a liquid crystal display module and also a liquid crystal display module itself implementing such a device and method.
2. Description of the Related Art
Liquid crystal displays are well known using a two-dimensional array of liquid crystal cells in which the cells share a plurality of signal lines in one direction and are selectively enabled by gate lines in a perpendicular direction. Drive circuits are provided which use the gate lines to enable respective sets of liquid crystal cells. The signal lines are then used to provide video signal levels to the enabled cells to charge those cells to the level required to give those cells their desired brightness.
It is usual to group the liquid crystal cells together to form image pixels. Each image pixel would typically include three liquid crystal cells corresponding respectively to red, green and blue. The red, green and blue liquid crystal cells of a pixel are provided on the same gate line and, indeed, can be driven by the same video signal. In particular, with a gate line enabling all of the liquid crystal cells of the pixel, the video signal is provided first to the red liquid crystal cell by means of its signal line, then to the green liquid crystal cell by means of its signal line and finally to the blue liquid crystal cell by means of its signal line.
Previously, it has been known to provide liquid crystal display modules with photo diodes around the liquid crystal display itself. The photo diodes may be provided separately from the module or may be constructed as part of the module, for instance in the liquid crystal display panel itself. The photo diodes provide an indication of the level of ambient light and allow improved control of the liquid crystal display module. For example, where the liquid crystal display module includes a back light for providing light through the liquid crystal display cells of the liquid crystal display, the brightness of the back light can be varied according to the detected level of ambient light.